1. Field of the Invention
This invention relates to light-emitting compounds or compositions and light-emitting devices that include the light-emitting compounds or compositions.
2. Description of the Related Art
Organic light-emitting devices (OLEDs) have been widely developed for flat panel displays, and are moving fast towards solid state lighting (SSL) applications. Organic Light Emitting Diodes (OLEDs) comprise a cathode, a hole transporting layer, an emissive layer, an electron transporting layer, and an anode. Light emitted from an OLED device is the result of recombination of positive charges (holes) and negative charges (electrons) inside an organic (emissive) layer. The holes and electrons combine within a single molecule or a small cluster of molecules to generate excitons, which are molecules in an excited state, or groups of organic molecules bound together in an excited state. When the organic molecules release the required energy and return to its stable state, photons are generated. The organic compound or group of compounds which emit the photons is referred as an electro-fluorescent material or electro-phosphorescent material depending on the nature of the radiative process. Thus the OLED emissive compounds may be selected for their ability to absorb primary radiation and emit radiation of a desired wavelength. For blue emitters, for example, emission within principle emission bands of 440 to 490 nm is desirable.
SSL applications may require white OLED device to achieve greater than 1,500 μm brightness, a color rendering index (CRI) greater than 70, and an operating time greater than 100,000 hours at 1,000 μlm/w. There are many approaches for generating white light from an OLED, but two common approaches are: direct combination of red, blue, and green light using either lateral patterning or vertical stacking of three emitters; and partial down conversion of blue light in combination with yellow phosphors. Both of these common approaches may be more effective if a highly efficient chemical- and photo-stable blue dye is employed. However, blue emitters may be less stable than dyes which emit other colors. Furthermore, and there are very few blue emitting devices showing CIE y value below 0.2 yet still with respectable efficiency. Thus, the development of deep blue emitters with good stability and high luminescence efficiency is desirable to effectively reduce power consumption and generating emission of different colors.
Diphenyl acetylene compounds have been used as additives in organic photoreflective polymer composites for electrooptic, photorefractive and liquid crystal applications (see for example, US 2006/0050354 and US 2006/000363). Thompson, et al (U.S. Pat. No. 6,210,814) described a polarization dopant molecule that contributed to the local dipole moment to spectrally shift the emission of a separate emissive dopant. Thompson, et al (U.S. Pat. No. 6,045,930) describes a [tris-diphenylacetylene amine] compound However, none of these compounds were described as blue emitting fluorescent compounds. Thus, the development of deep blue emitters with good stability and high luminescence efficiency is desirable to effectively reduce power consumption and generating emission of different colors.